Advanced imaging use and delays among inpatients with psychiatric comorbidity

Abstract Objective To determine whether presence of a psychiatric comorbidity impacts use of inpatient imaging tests and subsequent wait times. Methods This was a retrospective cohort study of all patients admitted to General Internal Medicine (GIM) at five academic hospitals in Toronto, Ontario from 2010 to 2019. Exposure was presence of a coded psychiatric comorbidity on admission. Primary outcome was time to test, as calculated from the time of test ordering to time of test completion, for computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, or peripherally inserted central catheter (PICC) insertion. Multilevel mixed‐effects models were used to identify predictors of time to test, and marginal effects were used to calculate differences in absolute units (h). Secondary outcome was the rate of each type of test included. Subgroup analyses were performed according to type of psychiatric comorbidity: psychotic, mood/anxiety, or substance use disorder. Results There were 196,819 GIM admissions from 2010to 2019. In 77,562 admissions, ≥1 advanced imaging test was performed. After adjusting for all covariates, presence of any psychiatric comorbidity was associated with increased time to test for MRI (adjusted difference: 5.3 h, 95% confidence interval [CI]: 3.9–6.8), PICC (adjusted difference: 3.7 h, 95% CI: 1.6–5.8), and ultrasound (adjusted difference: 3.0 h, 95% CI: 2.3–3.8), but not for CT (adjusted difference: 0.1 h, 95% CI: −0.3 to 0.5). Presence of any psychiatric comorbidity was associated with lower rate of ordering for all test types (adjusted difference: −17.2 tests per 100 days hospitalization, interquartile range: −18.0 to −16.3). Conclusions There was a lower rate of ordering of advanced imaging among patients with psychiatric comorbidity. Once ordered, time to test completion was longer for MRI, ultrasound, and PICC. Further exploration, such as quantifying rates of cancelled tests and qualitative studies evaluating hospital, provider, and patient barriers to timely advanced imaging, will be helpful in elucidating causes for these disparities.


BACKGROUND
There is a bidirectional association between mental and physical health disorders, such that individuals with mental health disorders are at greater risk of common chronic medical conditions, such as hypertension, diabetes, and chronic obstructive pulmonary disease (Lin et al., 2011;Scott et al., 2016;Sporinova et al., 2019;Surveillance & Epidemiology Division, Public Health Agency of Canada et al., 2015).A study of individuals from 17 countries demonstrated an independent association between mental and physical health conditions; for example, depression was associated with an increased odds of subsequent onset of hypertension, arthritis, and lung disease (Scott et al., 2016).
Individuals with chronic medical conditions also have an increased risk of psychiatric conditions like depression and anxiety (Sporinova et al., 2019;Surveillance & Epidemiology Division, Public Health Agency of Canada et al., 2015).A study of nearly 1 million Canadians with common chronic medical conditions showed that 15.8% had a concomitant mental health disorder (Sporinova et al., 2019).Psychiatric illnesses are independently associated with increased risk of cardio-and cerebrovascular disease (Lambert et al., 2022;Vance et al., 2019).Patients with psychiatric comorbidities, compared with those without, have increased medical costs, longer length of stay, and higher rates of readmission, nosocomial infection, and postoperative complications (Beeler et al., 2020;Bressi et al., 2006;Chwastiak et al., 2014;Daratha et al., 2012;Daumit et al., 2006;Druss et al., 2001;Jansen et al., 2018;Sporinova et al., 2019).
In addition, patients with psychiatric illness may be less likely to receive standard treatments for common medical conditions (Daumit et al., 2006;Druss et al., 2001).Patients with psychiatric illness were less likely to receive reperfusion therapy and guideline-based medical therapy (i.e., aspirin, beta-blocker, and angiotensin-converting enzyme inhibitor) after a myocardial infarction (Druss et al., 2001), had higher adjusted mortality rates, and were less likely to follow up with a cardiologist (Kurdyak et al., 2012).Similarly, patients with stroke and psychiatric comorbidity have lower rates of thrombolysis, carotid artery revascularization, rehabilitation attendance, and treatment with antiplatelet and lipid-lowering medications (Bongiorno et al., 2018(Bongiorno et al., , 2019;;Kapral et al., 2021).
Advanced imaging tests and radiological procedures, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and peripherally inserted central catheter (PICC) insertion, are commonly used to aid in both diagnosis and management of medical inpatients (Smith-Bindman et al., 2019;Verma et al., 2017).Given the finite resources in hospital, wait times for these tests can be prolonged (Cournane et al., 2016).While there is ample evidence that the care provided in hospital to patients with psychiatric illness is different than for patients without psychiatric illness, this is the first study, to our knowledge, to evaluate whether the use of inpatient imaging and associated waiting time is impacted by the presence of a psychiatric comorbidity.We have previously shown that delays in advanced imaging are associated with longer length of stay in hospital (Bartsch et al., 2023); therefore, disparities in wait times for advanced imaging between patients with and without psychiatric comorbidity could serve as one explanation for longer length of stay observed among patients with psychiatric comorbidity.
The objective of our study was to determine whether the use of advanced imaging, as well as the subsequent waiting time, differs between patients with and without a coded psychiatric diagnosis.Previous studies have shown that patients with psychiatric comorbidity experience differences in their hospitalization, ranging from likelihood of receiving guideline-based treatments to length of stay (Beeler et al., 2020;Bressi et al., 2006;Daumit et al., 2006;Druss et al., 2001;Sporinova et al., 2019); however, it has yet to be established whether medical imaging is yet another dimension of care that is impacted by the presence of a psychiatric comorbidity.Identifying differences may suggest an additional inequity in patient care and resource allocation, and underline the need to explore causes and potential solutions for this disparity.

Setting, study design, and data sources
We completed a retrospective cohort study of patients admitted to General Internal Medicine (GIM) in Toronto, Ontario, using the General Internal Medicine Inpatient Initiative (GEMINI) database, which includes all admissions to GIM at five academic hospitals affiliated with the University of Toronto (Verma et al., 2017).
GEMINI contains patient-level clinical data from each hospital, including information that is coded for submission to the Cana-

Participants
The cohort included all patients admitted to and discharged from the GIM service between April 1, 2010 and December 31, 2019 at the five academic health centers included within GEMINI.

Exposure
The primary exposure was having a coded psychiatric comorbidity on admission (Canadian Institute for Health Information, 2015).We utilized a definition generated by Ontario Health (formerly Health Quality Ontario) to measure mental health and addictions-related health service utilization (Brien et al., 2015;Health Quality Ontario, n.d.).The

Outcome measures
The primary outcome was time to test, in hours, as calculated from the time of ordering to the time of test completion.The secondary outcome was the rate of each type of included test, per 100 patient-days.Our data set did not include any tests that were ordered but not completed (cancelled).

Other variables
We included test  (Escobar et al., 2008;Quan et al., 2011;Statistics Canada Catalogue, 2017).Physician-level variables included gender, years in practice, whether the MRP was a general internist/hospitalist versus a subspecialist, and their annual GIM patient volume.

Statistical analysis
Demographic data were expressed as means with standard deviations (SD), counts, and frequencies.We compared patients with and without a coded psychiatric comorbidity using standardized mean differences (SMDs) given large sample sizes in GEMINI.An SMD >0.1 is considered meaningful (Austin, 2009).We reported the use of advanced imaging based on the volume of tests ordered, test type, tests per patient, time to test completion, time from admission to test ordering, and the proportion of hospital days spent waiting for a test.
For each of the four test types (CT, MRI, ultrasound, or PICC), we used separate mixed-effect negative binomial models with random intercepts at the admission, patient, and physician levels (with crossed random intercepts between patients and physicians) to measure the association between psychiatric comorbidity and time to test.
Random intercepts accounted for clustering of tests at the admission, patient, and physician levels.Patients who had at least one advanced imaging test performed after admission were included in this analysis (Figure S1).We performed prespecified stratified analyses according to type of psychiatric comorbidity (mood and anxiety disorders, psychotic disorders, and substance-related disorders).
We reported adjusted time to test as a difference in hours and adjusted rate of tests ordered, or average marginal effects, obtained using the "margins" package in R (CRAN, 2021).Average marginal effects are calculated as the mean of partial derivatives of the regression model with respect to each variable and each observation in the data-in contrast with marginal effects at the mean, average marginal effects have the advantage of keeping all other variables at their naturally observed values (Norton et al., 2019).
Multivariable Poisson models with the log of length of stay as an offset were also used to identify predictors of the rate of tests ordered per 100 days hospitalized, the secondary outcome.The cohort in this analysis included all admissions, regardless of whether a test was ordered.
For patients who had any days designated as alternate level of care (ALC) (Health Analytics Branch, Ministry of Health and Long-Term Care, 2017), which are days spent waiting for a discharge destination, we subtracted the number of ALC days from the total "days hospitalized" denominator for this outcome.As ALC days are, by definition, periods when patients are medically inactive, we removed these days from our calculation to avoid artificially lowering the rate of tests ordered.
All statistical analyses were performed using R version 4.0.2.

Ethics approval
Research Ethics Board approval was obtained from St. Michael's Hospital on behalf of all participating hospitals (Study ID 15-087), with a waiver of patient consent for this retrospective study using routinely collected health data.

Study cohort
From

Testing volumes
A total of 41.8% of patients with psychiatric comorbidity had at least one advanced imaging test performed during admission, which was similar for patients without psychiatric comorbidity (38.9%,SMD: 0.06) (Table 1).The mean number of tests performed during admission was similar (SMD: 0.07) for patients with psychiatric comorbidity (mean: 0.81, SD: 1.53) than for those without (mean: 0.70, SD: 1.33) (Table 1).
Across both groups, the most common test ordered was CT (51.5% of all tests for patients with psychiatric comorbidity and 52.1% for patients without), followed by ultrasound (30.5% of all tests for patients with psychiatric comorbidity and 30.9% for patients without) (  S1b).For all test types, there were no significant differences between patients with mood and anxiety disorders and patients without psychiatric comorbidity (SMD: 0.05) (Table S1c).

Rate of testing
The unadjusted rate of testing was not significantly different between patients with and without a psychiatric comorbidity (7.0 per 100 patient-days hospitalized vs. 8.9 per 100 patient-days hospitalized, respectively, p < .001)(Table 2).After adjusting for all covariates, the presence of any psychiatric comorbidity was associated with a reduced rate of testing for all test types (adjusted difference:

DISCUSSION
In this population-based cohort study of GIM hospitalizations, we found that presence of any psychiatric comorbidity was associated with increased wait times for advanced imaging, and that this effect was most pronounced in patients with psychotic illness.Furthermore, the rate of test ordering for all test types was lower for patients with psychiatric comorbidity.
Most patients with psychiatric illness have comorbid medical conditions, and the presence of psychiatric illness is associated with increased healthcare utilization and costs (longer length of stay, higher readmission rates) (Bressi et al., 2006;Chwastiak et al., 2014;Daratha et al., 2012;Jansen et al., 2018;Sporinova et al., 2019;Sprah et al., 2017).Furthermore, there is ample evidence that patients with psychiatric comorbidity experience more adverse outcomes and receive differential treatment in hospital, as compared to patients without psychiatric illness (Bongiorno et al., 2019;Daumit et al., 2006;Druss et al., 2001;Kurdyak et al., 2012).As examples, such patients are less likely F I G U R E 1 Adjusted time to test (h, 95% confidence interval) comparing patients with any psychiatric comorbidity and with specific psychiatric comorbidity (substance use disorder, mood and anxiety disorder, and psychotic disorder) to patients with no psychiatric comorbidity.CT, computed tomography; PICC, peripherally inserted central catheter; MRI, magnetic resonance imaging.
Our study demonstrates that radiological procedures are another facet of care that is impacted by the presence of psychiatric illness.
We found that having a coded psychiatric comorbidity was associated with significantly longer wait times for MRI, PICC, and ultrasound.
This effect was amplified in patients with psychotic illness, who experienced delays for all test types, and with greater degrees of delay.This may reflect increased severity of mental illness in patients with psychosis, and subsequent challenges in obtaining consent and completing advanced imaging tests.In contrast to our general finding of increased wait times for patients with psychiatric comorbidity, the presence of a substance use disorder was associated with decreased time to test for CT.This may be related to presentation with decreased level of consciousness or altered mental status in the setting of substance use, for which urgent neurological imaging is often performed.
We observed longer wait times for patients with psychiatric comorbidity.Furthermore, there was a lower rate of testing among patients with psychiatric comorbidity, which may reflect more cancelled tests in this patient group, as opposed to systematic discrepancies in ordering practice.Unfortunately, our data sources only included completed tests.It is well established that inpatients with psychiatric comorbidity are more likely to be prematurely discharged ( Brook et al., 2006;Simon et al., 2020).One qualitative study of patients with substance use disorders, for example, elucidated specific reasons for self-discharge, which included undertreated withdrawal, ongoing substance use cravings, and feeling discriminated against and stigmatized by the healthcare team (Simon et al., 2020).In light of these findings, it is foreseeable that patients with psychiatric comorbidity may be less likely to proceed with a test-for example, due to anxiety, paranoia, or claustrophobia.Interestingly, provider variables have also been shown to impact likelihood of premature discharge (Doktorchik et al., 2019).Extrapolating these to completion of inpatient imaging tests, limitations in orienting patients to the plan for hospitalization and establishing a supportive patient-provider relationship may decrease the likelihood of patients having tests completed expediently (Brook et al., 2006).
To help address disparities between patients with and without psychiatric comorbidity, rates of cancelled tests should be quantified and qualitative studies exploring mechanisms for cancelled, delayed, and re-ordered tests should be conducted.
This study employed a large, population-based sample, which enabled characterization of the impact of any psychiatric comorbidity, as well as specific subtypes of psychiatric illness, on the use of advanced imaging and subsequent wait times at five academic hospitals in Toronto, Ontario.As such, our findings are generalizable to other urban centers.Some limitations of our study warrant emphasis.
First, the indication for imaging tests ordered was unavailable.Given tests with urgent indications are prioritized, we attempted to mitigate this unknown by accounting for illness severity (using the LAPS) and most common admission diagnoses.Second, our data sources only captured completed tests and did not include tests that were ordered and subsequently canceled.This may have resulted in falsely shortened wait times-for example, when a test is cancelled and re-ordered by the medical imaging department at the time of test.Third, we used ICD-10-CA codes to identify patients with psychiatric illness.Previous studies reported that using ICD codes, in comparison to the reference standard of chart review, has excellent specificity but only low or moderate sensitivity in detecting depression ( Doktorchik et al., 2019;Fiest et al., 2014).Another study calculated positive and negative predictive values of 77% and 76%, respectively, for various psychiatric illnesses detected by ICD-9 codes, with the reference being patient self-reported mental health condition (Frayne et al., 2010).Missed identification of patients with psychiatric comorbidity could therefore be diluting effect sizes in our study.We did not have information about the duration or severity of psychiatric illness, which presumably could impact patient ability and/or willingness to communicate symptoms and participate in tests.Lastly, we were unable to report important information that was not readily available in electronic clinical and administrative data, such as smoking status.Presence of smoking may be an indication for imaging (i.e., to evaluate for malignancy) and is also a reason patients may leave hospital with tests pending or may not be in their room when called to imaging tests.
In summary, our study shows that presence of a psychiatric comorbidity is associated with increased wait times for common advanced imaging tests.For all test types studied, we identified a lower test-ing rate for patients with coded psychiatric comorbidities compared to those without.Further exploration, such as quantifying rates of cancelled tests and qualitative studies evaluating hospital, provider, and patient barriers to timely advanced imaging, will be helpful in elucidating causes for these disparities.
April 1, 2010 to December 31, 2019, 196,819patients were admitted to GIM.About half (49.2%) were women and the median age was 71 years old (Table1).A total of 18.4% had a comorbid psy- Table 2).More tests were ordered within the first day of admission went more abdominal ultrasounds (28.2% of all tests vs. 20.0%,SMD: 0.19) and fewer thoracic CTs (13.9% of all tests vs. 18.7%,SMD: 0.13) (Table Baseline characteristics of patients admitted to General Internal Medicine at five academic hospitals in Toronto, Ontario from April 1, 2010 to December 31, 2019.
TA B L E 1 Tests ordered for patients with psychiatric comorbidity, including by subgroup of psychiatric illness, and without psychiatric comorbidity.Note: Values are numbers (percentages) unless stated otherwise.Abbreviations: CT, computed tomography; IQR, interquartile range; MRI, magnetic resonance imaging; PICC, peripherally inserted central catheter; SMD, standardized mean difference.a Q1 is lowest income and Q5 is highest income.b Q1 is highest level of deprivation and Q5 is lowest level of deprivation.
TA B L E 2